It has been known for some time that various semiconductor materials can be formed in very thin layers so that energy levels within the material are limited to discrete energy levels. By depositing several very thin layers of different material in overlying relationship, devices, such as light emitting or light sensing diodes, can be formed. An example of such structures is disclosed in U.S. Pat. No. 5,079,601, entitled "Optoelectronic Devices Based on Intraband Transitions in Combinations of Type I and Type II Tunnel Junctions", issued Jan. 7, 1992.
In some instances, attempts have even been made to form several very thin layers of different semiconductor material into three terminal devices, or transistors. One such attempt is disclosed in an article by N. Yokoyama et al., entitled "Resonant-Tunneling Hot Electron Transistor", Solid-State Electronics, Vol/.31, No., pp. 577-582, 1988, printed in Great Britain. In the disclosed device, layers of material are formed in vertical overlying relationship to produce a collector on the bottom, an emitter on the top and a base positioned therebetween similar to the well known vertical semiconductor transistor manufactured throughout the world. Because of the vertical positioning, base, emitter and collector connections and terminals are difficult to provide. While there are some differences in operation and while this hot electron transistor is vertically very thin, there is very little improvement in manufacturing difficulty and very little saving in chip real estate.
A second attempt at producing a new transistor is disclosed in an article by M. A. Reed et al., entitled "Realization of a three-terminal resonant tunneling device: The bipolar quantum resonant tunneling transistor", Appl. Phys, Lett., 54 (11), pp 1034-1036, 13 Mar. 1989. In this structure, a quantum well is formed by layers of very thin material and the quantum well is biased as a base of the transistor. This structure is very difficult to realize in a manufacturing scenario and is quite similar to the above described transistor.